This invention relates to a vertical synchronizing signal detector circuit, and more particularly to a vertical synchronizing signal detector circuit for use in a PCM recording/reproducing system which may record and reproduce an audio signal with pulse code modulation by using a home VTR system or a part thereof, in accordance with EIAJ Technical File STC-077, Home PCM Encorder/Decorder.
The conventional vertical synchronizing signal detection has been effected either by detecting the envelope wave obtained by integrating a vertical synchronizing signal as used in a television receiver and so forth or by extracting the features of a vertical synchronizing signal such as its pulse width, period, etc.
With such a conventional method alone, however, a drop-out or the like may cause the synchronizing signal to be out of timing. In a PCM recording/reproducing system with a video tape recorder, data will be discontinous if a timing error of the synchronizing signal exceeds the length of a whole horizontal period. With a method wherein left-channel data, right-channel data and corrective data at the same instant are recorded separately with each other, an error correction can be made when the data in either channel are in error, but the discontinuity of data due to the above-mentioned timing error of the synchronizing signal will cause an erroneous correction for data during the error correction.